From fca03f175902fe899a87872228bf69c1b43a8543 Mon Sep 17 00:00:00 2001
From: Matt Sturgeon <matt@sturgeon.me.uk>
Date: Tue, 19 May 2026 14:42:10 +0100
Subject: [PATCH] lib: allow instantiating without a flake instance

Separate `overlay.nix` and `overlay.internal.nix`, to encapsulate the
`flake` argument. This allows non-flake users to import `./overlay.nix`
without providing a dummy `flake = null` attr.

The read-only `config.flake` option is only defined by `evalNixvim` when
`lib` is extended using the overlay in Nixvim's flake outputs.
---
 docs/lib/index.md        |  3 ++-
 flake/lib.nix            |  2 +-
 lib/modules.nix          |  6 +++---
 lib/overlay.internal.nix | 42 ++++++++++++++++++++++++++++++++++++++++
 lib/overlay.nix          | 39 +++----------------------------------
 lib/top-level.nix        |  2 +-
 6 files changed, 52 insertions(+), 42 deletions(-)
 create mode 100644 lib/overlay.internal.nix

diff --git a/docs/lib/index.md b/docs/lib/index.md
index 8931435f..7627beb0 100644
--- a/docs/lib/index.md
+++ b/docs/lib/index.md
@@ -84,7 +84,8 @@ When Nixvim is built in standalone mode, it expects `lib` to have Nixvim's exten
 If you'd like to use a `lib` with your own extensions, you must supply it via `specialArgs`,
 however you must ensure Nixvim's extensions are also present.
 
-This can be achieved using the lib overlay, available via the `<nixvim>.lib.overlay` flake output.
+This can be achieved using the lib overlay, available via the `<nixvim>.lib.overlay` flake output
+or importing the `lib/overlay.nix` file.
 
 ```nix
 # Example flake
diff --git a/flake/lib.nix b/flake/lib.nix
index bee5147a..66921d4c 100644
--- a/flake/lib.nix
+++ b/flake/lib.nix
@@ -14,7 +14,7 @@
       # on pinning the flake-parts nixpkgs-lib to the nixpkgs pin
       inherit (inputs.nixpkgs) lib;
     };
-    overlay = import ../lib/overlay.nix {
+    overlay = import ../lib/overlay.internal.nix {
       flake = self;
     };
     # Top-top-level aliases
diff --git a/lib/modules.nix b/lib/modules.nix
index 95cf5f82..c0739ec8 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -1,7 +1,7 @@
 {
   lib,
   self,
-  flake,
+  flake ? null,
 }:
 let
   removed = {
@@ -34,10 +34,10 @@ in
     lib.evalModules {
       modules = modules ++ [
         ../modules/top-level
-        {
+        (lib.optionalAttrs (lib.isAttrs flake) {
           _file = "<nixvim-flake>";
           flake = lib.mkOptionDefault flake;
-        }
+        })
         (lib.optionalAttrs (system != null) {
           _file = "evalNixvim";
           nixpkgs.hostPlatform = lib.mkOptionDefault { inherit system; };
diff --git a/lib/overlay.internal.nix b/lib/overlay.internal.nix
new file mode 100644
index 00000000..2f20c9f7
--- /dev/null
+++ b/lib/overlay.internal.nix
@@ -0,0 +1,42 @@
+/**
+  Internal function returning Nixvim's Nixpkgs `lib` overlay.
+
+  Publicly accessible at `./overlay.nix` and the `nixvim.lib.overlay` flake output.
+*/
+{ flake }:
+
+/**
+  Overlay function extending the Nixpkgs `lib` with Nixvim's additions.
+
+  This function is intended to be passed to `lib.extend`.
+
+  # Examples
+
+  Importing the file directly:
+  ```
+  lib.extend (import (nixvim + "/lib/overlay.nix"))
+  ```
+
+  Using the overlay from flake outputs:
+  ```
+  lib.extend nixvim.lib.overlay
+  ```
+
+  # Inputs
+
+  `lib`
+  : The final lib instance; the fixpoint of all extensions, including this one.
+
+  `prevLib`
+  : The lib instance prior to applying this overlay.
+*/
+lib: prevLib: {
+  # Add Nixvim's section to the lib
+  nixvim = import ./top-level.nix { inherit flake lib; };
+
+  # Extend the maintainers set with Nixvim-specific maintainers
+  maintainers = prevLib.maintainers // import ./maintainers.nix;
+
+  # Extend lib.types with Nixvim's custom types
+  types = prevLib.types // import ./types.nix { inherit lib; };
+}
diff --git a/lib/overlay.nix b/lib/overlay.nix
index ac76f151..e9ed5ce5 100644
--- a/lib/overlay.nix
+++ b/lib/overlay.nix
@@ -1,37 +1,4 @@
-{ flake }:
-
-/**
-  Overlay function extending the Nixpkgs `lib` with Nixvim's additions.
-
-  This function is intended to be passed to `lib.extend`.
-
-  # Examples
-
-  Importing the file directly:
-  ```
-  lib.extend (import ./overlay.nix { flake = nixvim; })
-  ```
-
-  Using the overlay from flake outputs:
-  ```
-  lib.extend nixvim.lib.overlay
-  ```
-
-  # Inputs
-
-  `lib`
-  : The final lib instance; the fixpoint of all extensions, including this one.
-
-  `prevLib`
-  : The lib instance prior to applying this overlay.
-*/
-lib: prevLib: {
-  # Add Nixvim's section to the lib
-  nixvim = import ./top-level.nix { inherit flake lib; };
-
-  # Extend the maintainers set with Nixvim-specific maintainers
-  maintainers = prevLib.maintainers // import ./maintainers.nix;
-
-  # Extend lib.types with Nixvim's custom types
-  types = prevLib.types // import ./types.nix { inherit lib; };
+# Public non-flake entrypoint for Nixvim's Nixpkgs-lib overlay
+import ./overlay.internal.nix {
+  flake = null;
 }
diff --git a/lib/top-level.nix b/lib/top-level.nix
index a27bb0ec..e603d3e5 100644
--- a/lib/top-level.nix
+++ b/lib/top-level.nix
@@ -16,7 +16,7 @@
 */
 {
   lib,
-  flake,
+  flake ? null,
 }:
 lib.makeExtensible (
   self: